1. Field of the Invention
The present invention relates to a hydrophilic substrate surface structure and the preparation method thereof, more particularly relates to a method for creating a stable long-term hydrophilic poly(dimethylsiloxane) PDMS surface. PDMS shows unstable surface chemistry which is characterized by hydrophobicity recovery. The creation of a stable hydrophilic PDMS surfaces is important for various applications.
2. Description of the Related Art
The substrate surface treatment is an important research topic in material science because it gives the substrate more desirable surface properties, ex. corrosion resistance, biomolecule adsorption resistance, and anti-oxidization, which are able to slow down the ageing of the material or make it more applicable.
With the development of biotechnology, the treatment of substrate surface is gaining attention as more biochemical materials are put into use. Biochemical materials include biochip substrates, cell culturing substrates and human implant materials. For example biochip substrates. These substrates can be made using silicon chips, glasses or polymers. Biochips may be used in medical testing, environmental testing, food testing, new drug development, basic research, military defense, and chemical synthesis. Biochips available in the present market are classified into gene chip, protein chip, and lab-on-a-chip. Lab-on-a-chip is designed according to the needs and are produced by various reactions on the chip. Currently, biochemical experiments that may be carried out on lab-on-a-chip include polymerase chain reaction (PCR) with gene amplification function, nucleic acid sequencing reaction, microfluidics, electrophoresis, mass spectrograph, antigen-antibody binding, and regular enzymatic reaction.
The microfluidic chip for biomedical testing fabricated by MEMS process offers the advantages of high performance, low sample consumption, low energy consumption, small size, and low cost. The design that integrates various procedures on the same chip provides a great potential and a market value.
For most materials used in applications such as biochips, cell culturing substrates or human implants, it is usually necessary to alter the surface characteristics by surface modification of the substrate. For example, poly(dimethylsiloxane) (PDMS), a widely used biomedical material exhibits unstable surface characteristics due to the recovery of hydrophobicity. Currently, the PDMS surface is typically modified by means of direct attachment of an in-situ generated polymer layer on to the PDMS surface or by dynamic coating on the PDMS. Those methods are simple, but the modified PDMS surface lacks long-term stability, which means it can not be exposed to air for a long periods of time and thus becomes unable to resist hydrophobicity recovery. The hydrophobicity recovery renders the surface unable to resist protein adsorption. Therefore, it is necessary to develop a widely applicable substrate surface modification method that can resist hydrophobicity recovery and impart long term hydrophilicity to the surface of the PDMS. This would give durability to various devices that are made of substrates that are usually unstable.